Evan Williams had the surprised but absolutely delighted look of a man who had just realised that the shiny stone in the ring that popped out of his cracker was actually a real diamond. He had just watched his charge Deep Purple confound his expectations by giving weight and a comprehensive beating to some quality rivals in the Peterborough Chase here yesterday. Now the temptation to take his new-found sparkler to the biggest Christmas party of all, the King George VI Chase, may prove irresistible.

"I didn't want to take on Kauto Star this season," the trainer said. "I'd hoped to run well here and then maybe go on to a race at Ascot in the new year. But now, I don't know. I suppose it would make sense to think about turning out again on Boxing Day."

It was both the style and substance of Deep Purple's performance that had the Welsh trainer shaking his head. Carrying a 10lb penalty for his narrow victory in the Charlie Hall Chase at Wetherby last month, he tracked the furious pace set by Herecomesthetruth, took the lead at the head of the final straight with two fences to go and seemed to engage a turbo gear under Paul Moloney on the run-in, powering six lengths clear of Tartak.

Afterwards, Williams kept trying to make sense of what he'd just seen from the eight-year-old. "I thought I had him bang on for the Charlie Hall," he said, "but he seems to have improved from there. He must have done, because the horse that won at Wetherby wouldn't have won here, not with that penalty.

"I couldn't have seen him winning like he's just done in my wildest dreams. But then, he did a piece of work on the grass on Saturday that was just ridiculous, better than anything from any horse we've had. In fact, it looked so good that I thought the other ones in the gallop were probably sick."

Deep Purple was one of last season's better novices, with three victories before a defeat by Tartak at Aintree. "He won a few good prizes but they weren't that hotly contested," said Williams. "He showed at Wetherby that he's very tough, but I really didn't think he had a performance like this one in him. But," he added, lapsing into technical terms, "he's absolutely bloody hosed up."

Yesterday's success was as much of a surprise to punters as Williams. Deep Purple's drift in the market, from 9-2 in the morning to an extraordinary 12-1, made the Marie Celeste seem a firmly anchored barge.

As well as producing his surge from the last fence, he was notably the only one in the field whose jumping held firm under the pressure applied by the pace round this flat, featureless but very fair oval. Something Wells fell; the well-backed favourite Tidal Bay made a ghastly blunder halfway round and did well almost to snatch third from Albertas Run; Herecomesthetruth, whose technique in the air was recklessly bold at times, finally unseated his rider at the last; Tartak lost lengths and precious momentum through errors. Racing Demon, twice a previous winner, jumped round safely on his return from a long absence, but never threatened.

Deep Purple, who carries the blue colours of Paul Green borne to victory most famously in the past by Hors La Loi in the Champion Hurdle seven years ago, impressed SkyBet most of the bookmakers, as a 10-1 shot to follow the likes of Best Mate, Edredon Bleu and One Man from victory here to the King George. "There is only a small window of opportunity for him to be in such form," said Williams. "We've never been ones to shirk a challenge and if he comes out of this race OK, then I expect we'll end up going to Kempton. Maybe it would be silly not to."

Tomorrow's chasing feature at Cheltenham, the Boylesports Gold Cup, brings together a field of 17, headed by the joint topweights Gwanako and Our Vic, with Atouchbetweenacara the 5-1 favourite. Today's star at the venue is the cross-country specialist Garde Champetre, who has the services of J T McNamara as he goes for his fifth success over the unique infield track. The gelding's regular pilot Nina Carberry switches to his stablemate Heads Onthe Ground, on whom McNamara cannot do the lighter weight.

Turf account: Sue Montgomery

Nap

Noble Alan (12.50 Doncaster) Exciting two-mile chasing recruit who can be forgiven a misjudgement last time. His technique was foot-perfect when he won on his debut.

Next best

Lidar (3.35 Cheltenham) Could not cope with today's rival Ghizao in a bumper on the course last month but it may be a different matter with hurdles to negotiate.

One to watch

Vino Griego (G L Moore) is steadily improving over hurdles and should find a race.

Where the money's going

Spanish Moon was the horse for money yesterday at the last hurrah of the international Flat season, cut a point to 6-1 by Paddy Power for Sunday's Hong Kong Vase.